Trend in Ionisation Energy down A Group

What happens as you go down a group?

Ionisation energies generally fall, making it easier to remove outer electrons

Why do ionisation energies fall as you go down the group?

Elements further down a group have extra electron shells compared to ones above.

What do extra shells mean?

The atomic radius is larger, which greatly reduces the attraction to the nucleus

What do the extra inner shells do?

Shield the outer electrons from the attraction of the nucleus.

What do the extra shells and inner shells make it easier to do?

To remove outer electrons, resulting in a lower ionisation energy.

What happens to the positive charge of the nucleus?

It increases as you go down a group, due to the extra protons, but this effect is overridden by the effect of the extra shells.